Computer systems commonly are sensitive to the behavior of devices coupled to the systems. Such effects include power management issues. Because power management has typically operated in a cooperative model, one badly behaving device can, by preventing a computer system from transitioning to an appropriate state of reduced power consumption, reduce the effectiveness of any or all platform power management mechanisms.
In one example, power in a computer system may be optimized utilizing low power states. Multiple different states with different levels of operation and power savings may be available. However, a processor of the computer system or any computer subsystem can remain stuck in a higher power state due to, for example, communication traffic generated by a device that is operating in an unnecessary or inopportune manner.
Many devices in current computer systems make use of PCI, PCI Express (PCIe), or Universal Serial Bus (USB, USB2) interconnects via on-board integration, integrated Mini-Card devices, ExpressCard slots, and/or USB walk-up ports. These interconnect standards, among others, are not in themselves optimized for power-friendly devices. Because of this, there may be a need for power efficient device design through use of traffic alignment, coalescing interrupts, and providing robust low power link state usage.